TweetFollow Us on Twitter

Jun 89 Letters
Volume Number:5
Issue Number:6
Column Tag:Letters

Letters

By David E. Smith, Editor & Publisher, MacTutor

Language Systems Plans

Rich Norling

Herndon, VA

In MacTutor’s April letters column, Bert Waggoner added his name to the list of those asking us to add a SELECT CASE statement to the Language Systems FORTRAN Compiler. We are now making plans for Version 2.0 and I want to let your readers know that SELECT CASE and NAMELIST are at the top of our list of new features to add. Both will be done according to the FORTRAN ’8X syntax, so no changes in FORTRAN source code will be needed when ’8X becomes a formal standard (let’s hope that happens before the proposed standard has to be renamed ’9X!).

Additional suggestions for new features in Language Systems FORTRAN are welcome. Please send them to us at the address listed in our ad (inside front cover).

Corrections

Don Koscheka

Arthur Young N0735

Joe,your article on adding windows to XCMDs was informative and, for the most part, well written. Your discussion of scroll bars needs clarification. You state that using ScrollRect to scroll a window is not the preferred approach because the window will not get redrawn until update time. This is not true. While Inside Macintosh does imply that you should pass the UpdateRgn of the current window to ScrollRect so that the vacated area gets accumulated into the window’s invalrgn, this is not strictly necessary. Consider the following code fragment:

 
Procedure TrackScroll( theControl : controlHandle; thePart : INTEGER 
);
VAR
    TempRgn     : Region;
    tempRect    : Rect;
    dh, dv      : INTEGER;
BEGIN
    {*** determine what part of the control we’re in... ***}
    {*** and set dh, dv accordingly                     ***}
    ...
 
    {*** now scroll the scrollable part of the window   ***}
    tempRect := theWindowsScrollablearea;
    TempRgn := newRgn;
 
    ScrollRect := ( tempRect, dh, dv, tempRgn );
    SetClip( tempRgn );
 
    {*** call whatever routine draws window contents    ***}
    Redraw_The_Window;
 
    DisposeRgn( tempRgn );
    ...
END;

This code has the advantage of requiring only enough extra memory to store the vacated region. Moreover, the novice programmer need not write any special screen drawing code. Whatever code is used to draw at update time can be called directly to redraw the window at scroll time. Since the window is clipped to only the vacated region, this approach results in fast, smooth scrolling.

The more experienced user can query the region to determine exactly which rectangle to update so that the application draws only what will be displayed in the vacated rectangle. This is useful in applications like word processors where much of the update time is spent calculating where things need to go on the screen.

Another interesting consideration is the possibility of creating universal scroll bars. We accomplished this by having track scroll operate on a “scroll record” that keeps track of all appropriate information relating to a given scroll bar. One of the fields passed to the scroll record is the address of the routine to call in lieu of “Redraw_the_Window” in the above example. The result is quite satisfactory: one pair of scroll bars can be made to behave consistently regardless of the number of window variations in a given application.

Thanks for the bent ear. Good luck at Apple (as a six-year veteran, I can tell you that it’s a great place to work...)

CDEF Corrections

Kirk Chase

Anaheim, CA

It was brought up to my attention of another way to include CDEFs for debugging purposes. James Plamondon, from Abacus Concepts, pointed out a better, more legal (?), way of setting the contrlDefProc field of the control record.

const
 JMP_Instruction = $4EF9;

type
 JumpRec = record
 instruction  :  integer;
 function : Ptr;
 end; {JumpRec}

 JumpPtr = ^JumpRec;
 JumpHdl = ^JumpPtr;

var
 cdefJump : JumpHdl;
 ctrlHdl : ControlHandle;

begin { Open_Example_Window}
 {allocate and initialize jump record}
 cdefJump := JumpHdl(NewHandle(sizeof(JumpRec)));
 cdefJump^^.instruction := JMP_Instruction;
 cdefJump^^.function := myCDEFProc;
 {this ends initializing the jump record}
 
 {get the control record}
 CtrlHdl := GetNewControl(ButtonID, MyWindow);
 
 {Set the contrlDefProc}
 CtrlHdl^^.contrlDefProc := Handle(cdefJump);
 
end;

After diving into the tech notes, I also found what James already knew. James also mentions that the control definition proc should be locked by keeping it in code segment 1.

I appreciate James Plamondon help. The method I gave was essentially for prototyping controls. This made development time faster since you could bypass the Compile, ResEdit, Compile, Frustration loop. I hope Abacus realizes the asset James Plamondon is. Thanks A Bunch.

MPW vs. LSC

Will Flor

Loves Park, IL

I thought I might give my views on the MPW vs. LSC controversy raging in the March issue of your excellent journal, and also report a serious error in Jerry Sweet’s otherwise excellent article on Ada.

In my last job, I developed finite-element modeling software on the Mac, and the project was started in LSC. This type of software uses a lot of file I/O, and we had a large set of routines known to work properly in several other environments (hundreds of units shipped without a single bug report dealing with file I/O). Upon porting these routines to LSC, they did not work. An examination of the problem showed the LSC libraries to be bug-ridden and unmaintainable. The errors we were getting included undocumented error codes being returned, “file not found” error code returned when we tried to create a file, and more. After wasting nearly a day, we ported to MPW 2.0.2 and never had these problems. The Think technical support people were not knowledgeable about their product, but admitted the sorry state of their libraries after the erroneous source lines were pointed out to them. I have heard other similar stories from other software developers, too. For very simple programs, perhaps LSC works adequately; for true big-time software development it simply doesn’t do the job. The “one segment per source file” restriction is untenable as well. I do not use LSC and cannot recommend it to my clients.

Comparing MPW 3.0 to LSC is like comparing a turbo SAAB to a tricycle--they do basically the same thing, and MPW (and SAAB) is arguably harder to learn to use properly, but there’s an obvious difference in power and capability. MPW 3.0 is so different from MPW 2.0.2 that it definitely warrants the upgrade fee, since it’s really a totally different product--the C compiler is totally different, the Projector source code control system is great (although it suffers from a few problems as well), and everything is 25-40% faster. Perhaps a tricycle is more appropriate for some, but I’ll take MPW and the turbo SAAB any day.

Jerry Sweet’s otherwise excellent article on Ada did contain one serious factual error. He states that the MPW C “integer” data type is 16 bits wide--it is 32 bits wide. The MPW C integral type that is 16 bits wide is “short integer” or simply “short.” This is crucial to writing a correct interface subprogram since, as he correctly points out, there is no data type cross-checking available, and it is easy to pass the wrong parameter type.

Thank you, Mr. Smith, for editing such an excellent journal. Please keep up the good work.

More On Compare Strings

John S. Stokes III

San Diego, CA

In Steve Brecher’s letter published in the March 1989 MacTutor, page 11, he pointed out a bug in my “Compare Strings” routine in addition to suggesting some improvements. I confess that I wrote the letter off the top off my head in response to seeing some wasteful code. In looking at the actual code from programs I’ve written, I do use the

 Moveq  #0,D0
 Move.B (A0),D0

technique to load up the length for the compare loop.

I agree that using

;2


@0 Cmp.B(A0)+,(A1)+
 DBne D0, @0

is much better than using

@10Cmp.B(A0)+, (A1)+
 Bne.S  @900
 Dbra D1, @10

and I thank Steve for pointing that out.

There is an error in his code if the comment “Return D0.L=1 if equal, 0 if not equal” is to be taken seriously. Consider what happens to register D0 if the strings compare equally. Register D0 will have a $0000FFFF after falling out of the loop. Executing

 Seq  D0

will cause D0 to still contain $0000FFFF since the FF will replace the existing low order FF. Executing

 Neq.B  D0

will cause D0 to contain $0000FF01 instead of $00000001. Ooops.

If the strings are not equal, D0 will contain $000000?? before the Seq instruction and $00000000 after both the Seq and Neg.B instructions. This is OK.

The solution is to change the Neg.B to a Neg.W.

A re-corrected CompareString routine would look like this:

;3

;A0 -> Pascal String 1
;A1 -> Pascal String 2
;D0 Returns D0.L=1 if equal, 0 if not equal
;Alters A0-A1

CompareString:

;4

 Moveq  #0,D0
 Move.B (A0),D0  ;gross length - 1
@0 Cmp.B(A0)+,(A1)+;loop until 
 DBne D0,@0 ; not equal or end
 Seq  D0;$0000ffFF if equal, else 0
 Neg.W  D0;1 if equal, else 0
 Rts

Also, Steve did err in saying:

“Ext.W propagates the value in bit 15 of the register through bits 16 31. Therefore, it will not have the desired effect of clearing bits 8 15. Ext.B would not work either for cases in which the string length is greater than 127, i.e., negative considered as a signed byte; in such cases Ext.B would set bits 8 15, making the unsigned word value very large.”

There is no “Ext.B” instruction. Ext.W does what was ascribed to Ext.B; Ext.L does what was ascribed to Ext.W. So my Ext.W instruction did have the desired effect as long as the string length was less than 128.

Correction to Correction to CompareString

Steve Brecher

Sunnyvale, CA

John F. Reisor’s letter (Apr. 1989) correcting John Stokes’s original (Jan. 1989) made me realize that my own correction (Mar. 1989) was incorrect! Reisor’s code contains an error also.

My submission omitted an Ext.B D0 instruction just before the final Rts. Reisor uses Ext.W D0 where there should be an Ext.B D0.

Since this issue of conditioning bits 8..15 of a register has tripped up three of us, perhaps a review is in order. Ext.B sets each of bits 8 through 15 of a register to be equal to bit 7; it does not affect bits 0..7 or bits 16..31. Ext.W sets each of bits 16..31 to be equal to bit 15; it does not affect bits 0..15. In other words, Ext.B extends the sign of the low order byte through the high order byte of the low order word. Ext.W extends the sign of the low order word through the high order word.

Note that where I wrote

 Seq  D0
 Neg.B  D0

Reisor wrote instead

 Sne  D0
 AddQ.B #1,D0

which is equivalent.

My routine and Reisor’s, after correction, are both the same length. But any Macintosh assembly language programmer should be able to come up with a version that is one word shorter--left as an exercise for the reader. For those who wish to try, here is the final “long” version:

;5

; A0 points to a Pascal string
; A1 points to a Pascal string
; Returns D0.L = 1 if strings equal, else 0

 MoveQ  #0,D0
 Move.B (A0),D0
@0 Cmp.B(A0)+,(A1)+
 Dbne D0,@0
 Seq  D0
 Neg.B  D0
 Ext.B  D0
 Rts

Claris CAD

Kirk Chase

Anaheim, CA

Claris has added another fine product to their line, Claris CAD. This is a fine CAD product, specifically designed to take advantage of the Mac and its graphic capability. This high-end product follows the trend of others by including a videotape for learning the program’s capabilities rapidly. It has a complete set of two-dimensional tools for design and drafting professionals. It also allows for changing dimensions and units.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Evernote 6.9.1 - Create searchable notes...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more
jAlbum Pro 13.5 - Organize your digital...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. You can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly... Read more
jAlbum 13.5 - Create custom photo galler...
With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly, with pro results - Simply drag and drop photos into groups, choose a design... Read more
Google Chrome 53.0.2785.143 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more
Chromium 53.0.2785.143 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 53.0.2785.143: [Security Fix] High CVE-2016-... Read more
QuickBooks 2015 16.1.7.1524 R8 - Financi...
Save 20% on QuickBooks Pro for Mac today through this special discount link QuickBooks 2015 helps you manage your business easily and efficiently. Organize your finances all in one place, track... Read more
Sierra Cache Cleaner 11.0.1 - Clear cach...
Sierra Cache Cleaner is an award-winning general purpose tool for macOS X. SCC makes system maintenance simple with an easy point-and-click interface to many macOS X functions. Novice and expert... Read more
Default Folder X 5.0.7 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more
Safari Technology Preview 10.1 - The new...
Safari Technology Preview contains the most recent additions and improvements to WebKit and the latest advances in Safari web technologies. And once installed, you will receive notifications of... Read more
Tweetbot 2.4.4 - Popular Twitter client.
Tweetbot is a full-featured OS X Twitter client with a lot of personality. Whether it's the meticulously-crafted interface, sounds and animation, or features like multiple timelines and column views... Read more

Cybird’s latest release - BFB Champions...
Launched in the UK in early September, BFB Champions’ newest update is loaded with great new features, and looks set to outshine the original version by taking it out of soft launch and giving it a new lease of life. | Read more »
3 apps to boost your focus
As someone who works from home, my workspace is a minefield of distraction. Cats, tasty snacks, the wind blowing past my window, that cleaning that I suddenly can’t put off any longer. If I let distraction takes its course, I find that soon half... | Read more »
4 games like Burly Men at Sea to inspire...
Burly Men at Sea is out today and it looks a treat. It tells the tale of three Scandinavian fishermen who leave the humdrum of their daily lives to go exploring. It’s a beautiful folksy story that unfurls as you interact with the environment... | Read more »
3 reasons you need to play Kingdom: New...
Developed by a tag team of indie developers - Thomas "Noio" van den Berg and Marco "Licorice" Bancale - Kingdom is a vibrant medieval fantasy adventure that casts players as a king or queen who must expand their empire by exploring the vasts lands... | Read more »
JoyCity have launched a brand new King o...
Great news for all of you Game of Dice fans out there - JoyCity have just released a brand new limited edition pack with a really cool twist. The premise of Game of Dice is fairly straightforward, asking you to roll dice to navigate your way around... | Read more »
Burly Men at Sea (Games)
Burly Men at Sea 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Burly Men at Sea is a folktale about a trio of large, bearded fishermen who step away from the ordinary to seek adventure. | Read more »
3 tips for catching the gnarliest waves...
Like a wave breaking on the shore, Tidal Rider swept its way onto the App Store charts this week settling firmly in the top 10. It’s a one-touch high score-chaser in which you pull surfing stunts while dodging seagulls and collecting coins. The... | Read more »
The beginner's guide to destroying...
Age of Heroes: Conquest is 5th Planet Games’ all new turn-based multiplayer RPG, full of fantasy exploration, guild building, and treasure hunting. It’s pretty user-friendly as far as these games go, but when you really get down to it, you’ll find... | Read more »
Infinite Tanks (Games)
Infinite Tanks 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: | Read more »
Agatha Christie - The ABC Murders (FULL)...
Agatha Christie - The ABC Murders (FULL) 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: Agatha Christie: The ABC Murders Your weapon is your knowledge. Your wits will be put to the ultimate... | Read more »

Price Scanner via MacPrices.net

15-inch Retina MacBook Pros on sale for $200...
B&H Photo has 15″ Retina Apple MacBook Pros on sale for $200 off MSRP. Shipping is free, and B&H charges NY tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799 $200 off MSRP - 15″ 2.5GHz Retina... Read more
Apple refurbished iMacs available for up to $...
Apple has Certified Refurbished 2015 21″ & 27″ iMacs available for up to $350 off MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: - 21″ 3.... Read more
Check Apple prices on any device with the iTr...
MacPrices is proud to offer readers a free iOS app (iPhones, iPads, & iPod touch) and Android app (Google Play and Amazon App Store) called iTracx, which allows you to glance at today’s lowest... Read more
Apple price trackers, updated continuously
Scan our Apple Price Trackers for the latest information on sales, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. We update the trackers continuously: - 15″... Read more
Apple refurbished 2016 13-inch MacBook Airs a...
Apple has Certified Refurbished 2016 13″ MacBook Airs available starting at $849. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2016 13″ 1.6GHz/8GB/128GB MacBook... Read more
1.4GHz Mac mini on sale for $449, save $50
Adorama has the 1.4GHz Mac mini on sale for $50 off MSRP including free shipping plus NY & NJ sales tax only: - 1.4GHz Mac mini (Apple sku# MGEM2LL/A): $449 $50 off MSRP To purchase a mini at... Read more
Apple refurbished 2015 13-inch MacBook Airs a...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $759. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2015 13″ 1.6GHz/4GB/128GB MacBook... Read more
MacBook Airs on sale for up to $100 off MSRP
B&H Photo has 13″ and 11″ MacBook Airs on sale for up to $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air: $799 $100 MSRP - 11″ 1.6GHz/256GB... Read more
Apple refurbished 12-inch 128GB iPad Pros ava...
Apple has Certified Refurbished 12″ Apple iPad Pros available for up to $160 off the cost of new iPads. An Apple one-year warranty is included with each model, and shipping is free: - 32GB 12″ iPad... Read more
Phone2Action Unveils New Voter Turnout Techno...
Phone2Action, a leading digital advocacy platform, today launched its Tech to Vote Civic Action Center digital advocacy and communications platform on National Voter Registration Day September 27.... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Restaurant Manager (Neighborhood Captain) - A...
…in every aspect of daily operation. WHY YOU'LL LIKE IT: You'll be the Big Apple . You'll solve problems. You'll get to show your ability to handle the stress and Read more
*Apple* Wireless Lead - T-ROC - The Retail O...
…wealth of knowledge in wireless sales and activations to the Beautiful and NEW APPLE Experience store within MACYS.. THIS role, APPLE Wireless Lead, isbrandnewas Read more
Lead *Apple* Advocate - T-ROC - The Retail...
…Company, is proud of its unprecedented relationship with our partner and client, APPLE ,in bringing amazing" APPLE ADVOCATES"to "non" Apple store locations. Read more
*Apple* Advocate - T-ROC - The Retail Outsou...
…Company, is proud of its unprecedented relationship with our partner and client, APPLE ,in bringing amazing" APPLE ADVOCATES"to "non" Apple store locations. Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.